Extrusion head for continuously extruding a compound strand of plastic materials

ABSTRACT

Apparatus for manufacturing a strongly integrated compound strand formed by pressing together at least two different plastic materials. A first extruded plastic strand is pressed through a hollow cylindrical die and a second extruded plastic strand is pressed through a generally radial passageway into an annular portion. A rotary part rotated about the axis of the cylindrical die includes a portion of the passageway for helically winding the second plastic strand into the first plastic strand.

United States Patent Meneidis Feb. 15, 1972 EXTRUSION HEAD FORCONTINUOUSLY EXTRUDING A COMPOUND STRAND OF PLASTIC MATERIALS Inventor:Petros G. Meneidis, Ahamae, Greece Assignec: Lavreotiki Societelndustrielle Anonyme,

Athens, Greece Filed: Feb. 4, 1969 Appl. No.: 796,509

Foreign Application Priority Data Feb. 14, 1968 Greece ..34082/68 Aug.21, 1968 Greece ..35413/68 U.S. Cl ..425/l09, 264/173, 264/209,

425/131, 425/381, 425/382 Int. Cl ..B29f 3/01, B29f 3/12, B32b 31/30Field of Search ..264/l71, 173, 209; 18/13 RR,

[56] References Cited UNITED STATES PATENTS 2,191,829 2/1940 Johnson..18/13 R 2,800,683 7/1957 Teichman FOREIGN PATENTS OR APPLICATIONS40/21432 9/1965 Japan ..264/l76 Smith 156/244 X Primary Examiner-RobertF. White Assistant Examiner-J. H. Silbaugh Attorney-Littlepage,Quaintance, Wray & Aisenberg [5 7] ABSTRACT Apparatus for manufacturinga strongly integrated compound strand formed by pressing together atleast two different plastic materials. A first extruded plastic strandis pressed through a hollow cylindrical die and a second extrudedplastic strand is pressed through a generally radial passageway into anannular portion. A rotary part rotated about the axis of the cylindricaldie includes a portion of the passageway for helically winding thesecond plastic strand into the first plastic strand.

4 Claims, 5 Drawing Figures EXTRUSION HEAD FOR CONTINUOUSLY EXTRUDING ACOMPOUND STRAND F PLASTIC MATERIALS The present invention relates toapparatus for manufacturing a strongly integrated compound strandarticle formed of at least two different plastic materials.

Compound strands formed of several polymer materials have beenmanufactured by individually pressing and gauging a number of strandswhich are brought together and joined to each other by gluing orwelding. Such methods have inter alia the disadvantage that they requirea great number of steps. Further, frequently the resulting extrusionpressed strand article does not form into a homogeneous strand.

Moreover, it was for the most part not possible to strengthen suchpressed strand articles with a polymer material. It was possible only tostrengthen such strands by textile or metallic weaves, individualthreads, cords or nets, embodied in a first polymer strand to besubsequently pressed with a second polymer strand. Apart from the factthat strengthened strand articles manufactured in this way are lesshomogeneous, such a method is complicated in the handling and joining oftwo materials which are fundamentally different in their properties,i.e., requires numerous steps to unite such materials. This isparticularly true in the manufacture of strengthened or reinforcedextrusion pressed hollow bodies, for example, pipes or flexible hoses.

The invention provides apparatus for carrying out a method which issimple and which requires a minimum of maintenance and which permitsgreat speed of manufacture and which produces a compound strandsubstantially free from the above-mentioned disadvantages.

The invention consists in apparatus for manufacturing a compound strandof at least two extrudable plastic materials by a method comprising:extruding a first plastic strand, extruding a second plastic strand, andhelically winding the second plastic strand about and into engagementwith the first plastic strand while both strands are being extruded andare in a plastic fluid state.

The invention further consists in an injection head for forming acompound strand of at least two extrudable plastic materials comprising:a body having a channel for feeding a first plastic strand and apassageway for feeding a second plastic strand into the said channel, arotary part arranged for rotation about the channel and including theportion of the said passageway adjacent to the channel, whereby uponrotating the rotary part the second strand is helically wound andpressed on to the first strand.

Preferably, the said passageway includes an annular portion and therotary part includes a vane having a profile corresponding to the crosssection of the said annular portion, so that upon rotation of the rotarypart the vane pushes the second strand through the said annular portioninto the portion ofthe passageway in the rotary part.

Preferably, the rotary part is disposed between two stationary parts androtatably mounted on one of the parts.

The invention further consists in apparatus for forming a compoundstrand wherein the first plastic strand has at least one physicalcharacteristic different from the second plastic strand.

Preferably, the first plastic strand has greater flexibility than thesecond plastic strand and the second plastic strand has greater strengththan the first plastic strand.

The above-mentioned physical characteristic may be the color, themechanical resistance or both.

The helical shape of the second strand helps retain the properties offlexibility in the finished compound strand, so that the second strandgives the finished hollow compound strand a particularly high-shapestability and strength to resist excessive internal pressures.

On the other hand, the differing physical characteristic property of thetwo strands may be only the color. The compound strand may be pressedabout an electric conductor to form insulation therefor. In such a case,a plurality of different dies, for example, four dies, various colorcombinations may be produced.

The invention will now be described with reference to the accompanyingdrawings, wherein:

FIG. 1 is a diagrammatic longitudinal section of a first embodiment ofan injection head,

FIG. 2 is a detail in longitudinal section ofa component part of theinjection head shown in FIG. 1,

FIG. 3 is an end view of the component part shown in FIG. 2, seen indirection of the arrow 3 in FIG. 2,

FIG. 3A shows an enlarged portion of the component of FIG. 3, and

FIG. 4 is a diagrammatic longitudinal section of a second embodiment ofthe injection head.

The injection head 10 shown in FIGS. l3 may be arranged as alongitudinal or transverse injection head, and forms the end of aconventional injection or extrusion press, i.e., a worm press, which ishereinafter called the irst extruder. In FIG. 1, the first extruder isdisposed to the right of the injection head 10, as illustrated inFIG. 1. Accordingly, the flow of material from the first extruder isfrom the right to the left as indicated by the arrow in FIG. 1.

The end portion 11 of the first extruder has a conically tapered bore 12for receiving a torpedo 13, which is integral with an injection mandrel14 arranged in the injection head 10. The end portion 11 includes anexternal screw thread 15 which is received in the die body, generallyindicated as 16, by a cooperating screw thread. The die body 16 includesthe first of the component parts, a plate 17, which threadedly engagesthe screw thread 15 and is therefore fixed relative to the firstextruder.

The plate 17 has a radial bore 18, with integral screwthreading forconnection with a second injection press, hereinafter called the secondextruder" (not shown). The base of the bore 18 communicates withpassageway 19 directed inwards which communicates with an inclinedpassageway 20, which in turn is in communication with an annular groove21 formed in the front face of the plate 17 and arranged concentricallywith respect to the injection mandrel 14. Accordingly, a strand ofplastics material from the second extruder pressed into the plate 17will pass through the threaded bore 18, the passageways 19 and 20 andonto the annular groove 21.

The annular groove is formed in the front face 23 of the plate 17 remotefrom the end of the first extruder and is ar ranged in the vicinity ofthe die channel 22 which passes through the entire die body 16.

Although the Figures of the drawings appear to show play between part 24and the plate 17, the part 24 and plate 17 abuts closely along face 23,as can be seen in FIGS. 2 and 3, and is connected for rotationtherewith. The part 24, as described in detail below, is connected forrotation by a ball bearing 25 disposed on a second plate 26, which isfixedly connected to the plate 17 by several bolts 27 (only one of whichis shown). The rotary part 24 is disposed between the stationary plates17 and 26. The main component parts 17, 24 and 26 of the die body havean internal bore which is coaxially spaced from the injection mandrel 14forming a hollow cylindrical gap 22 or die channel therebetween.

The periphery of the rotary part 24 is formed as a toothed gear 28 whichis arranged to mesh with a driven chain 29 which is showndiagrammatically in FIG. 1. The thickened hub 30 of the rotary part 24receives on one side the ball bearing 25, and on the other side adepression 31 engages, with as little play as possible, end face orfitting surface 23 of the plate 17. The rotary part 24 includes aninclined bore 32 which communicates with the annular channel or groove21 at one end and the die channel 22 at the other end. As can be seenfrom FIG. 3, the inclined bore 32 may run either in the same directionas the passageway 20 in the plate 17, as drawn in full lines; or it mayrun tangentially to the die channel 22, as shown in dotted lines. A vane33 is disposed in the immediate vicinity of the end of the bore 32,communicating with the annular channel 21, and formed on the rotary part24, although as shown in the drawing, the vane 33 fits as closely aspossible to the inner profile of the annular channel 21. Accordingly,when the rotary part 24 rotates, the vane 33 slides along the annularchannel 21.

The operation of the injection head shown in FIG. 1 is as follows: thefirst extruder (not shown) feeds a plastic material into the die channel22 and, at the same time, the second extruder feeds a second plasticmaterial into the bore 18 and then through passageways I9, 20, annulargroove 21 and bore 32. The direction of advance of the first extruder isdesignated as axial, and that of the second extruder as radial.

By rotating the rotary part 24 by the chain 29 anticlockwise, i.e., inthe direction of the arrow 34, the bore 31 rotates about the injectionmandrel 14. Accordingly the outlet orifice of the bore 32 rotatesrelative to the die channel 22 as the bore 18 rotates relative to theinjection mandrel 14.

Accordingly, the second strand is pressed radially into the axiallyflowing main strand, from a rotating position about the first strand.This in turn gives the second strand a helical shape, by the superimposition of the radial flow into the axial direction.

The two plastic strands are then pressed together by the followingmaterial through the part of the die channel 22 surrounding the plate26, and are accordingly gauged or calibrated, i.e., the second strandwhich is still in a fluid state is embedded in the first strand which isalso in a fluid state, so that the hollow tubular strand issuing fromthe end 35 of the die body 16 is homogeneous and uniform. The resultinghollow tubular strand can then be subjected to further operations,either immediately after leaving the die body 16 or at some later time.The resulting hollow tubular strand can accordingly be further used asflexible hose or tube or can be used as semifinished product forproducing bottles or cylinders by blow moulding or for pressing aroundan electric cable.

FIG. 4 will now be described. Note that the same reference numbers as inFIGS. 1 to 3 are used to indicate the similar elements whereverpossible. As in the first embodiment the end 11 of the first extruder issecured to the plate 17 by the screw thread 15.

In contrast to the first embodiment, the ball bearing 25 is disposedonto the cylindrical extension 36 of the plate 17. The plate 26 issecured to the plate 17. The bore 18 for receiving plastics materialfrom the second extruder is disposed in the plate 26, and communicateswith the passageway 19 which in turn communicates with an annular groove37 formed in the cylindrical wall 38 in the plate 26. This annulargroove 37 serves the same purpose as the annular groove 21 of FIG. 1.The difference is that the groove 37 in the second embodiment does notabut a flat surface against the rotary part 24. The rotary part 24 has ahollow cylindrical extension 39 rotatable relative to cylindrical wall38 with as little play as possible. A passageway 40 is formed in theextension 39 which communicates with the bore 32. This passageway 40 isfunnelshaped with the wide portion located opposite the annular groove37. A radial annular projection 41 is connected to the extension 39 andextends between cylindrical extension 36 and the plate 26. Theprojection 41 has a passageway therein which extends between thefunnel-shaped passageway 40 and the die channel 22.

In this embodiment, a vane 42 is constructed on the rotary part 24 andis shaped so that it conforms to the annular groove 37. Upon rotation ofthe rotary part 24, the vane 42 slides along the annular groove, wherebythe material located therein is continuously pushed forward, circulatedalong the groove 37 and then through the passageway 40. During rotationthere is substantially no relative movement which would subject thematerial to shearing or tangential stress.

As in the first embodiment, the second embodiment includes a pluralityof gear teeth 28 disposed along the periphery of the rotary part 24driven by a chain 29.

The second embodiment shown in FIG. 4 is to a certain extent the reverseof the first embodiment shown in FIGS. 1 to 3, with the furtherdifference that the transition place at which the second strand isforced into the rotary part 24 is along a curved surface, a cylinderwhile in the seco'ndembodiment the transition place is along a planarsurface in the first embodiment.

Moreover, the embodiment shown in FIG. 4, reference to the forcesoccurring in operation, is more advantageous than the embodiment shownin FIG. 1.

The injection head shown in FIG. 4 could also be simplified by omittingthe plate 17 and mounting a bearing for the rotary part 24 directly onthe end 11 of the first extruder. In this modification, it would inaddition be necessary to secure the plate 26 in a stationary position bysuitable means.

The operation of the injection head 10 illustrated in FIG. 4 is similarto that of FIGS. 1 to 3. In FIG. 4 the strand issuing from the firstextruder has light dotted shading and the second strand issuing from thesecond extruder has darker dotted shading. The finished or semifinishedhollow strand 43 leaving the end 35 of the injection head 10 is clearlyillustrated in FIG. 4 showing the helical mark second strand embedded inthe light first strand.

I claim:

1. In an extrusion head for continuously extruding a strand consistingof two different plastic materials:

an extrusion die converging into a cylindrical extrusion orifice forextruding a first plastic material;

at least one stationary member having an axial cylindrical openingaligned with and coaxial to said cylindrical orifice for receivingtherefrom a stream of said first plastic material, said stationarymember defining a fitting sur face;

an annular channel formed in said fitting surface of said stationarymember coaxially to said cylindrical opening and in outwardly spacedrelationship to the axial cylindrical opening in said stationary member,and a feed opening in said stationary member leading into said annularchannel for feeding a pressurized second plastic material into saidchannel;

a rotatable member mounted for coaxial rotation around said axialcylindrical opening and to snugly fit said fitting surface, a borewithin said rotatable member having a cylindrical wall flush with theinside surface of said axial cylindrical opening in said stationarymember;

a passageway in said rotatable member leading inwardly to saidcylindrical wall and outwardly to communicate with said annular channel;and a vane member formed on said rotatable member for rotationtherewith, said vane member snugly fitting into the inside of saidannular channel for continuously diverting upon rotation of saidrotatable member said pressurized second plastic material from saidannular channel into said passageway and forcing it therefrom into saidstream of first plastic material.

2. The extrusion head of claim 1, which has a stationary cylindricalmandrel coaxially disposed within the axial cylindrical opening andextending through the stationary member and through the rotatablemember.

3. In an extrusion head for continuously extruding a stream consistingof two different plastic materials:

an extrusion die having a die passage converging into a cylindricalextrusion orifice for extruding a first plastic material,

two stationary members having each an axial cylindrical opening alignedwith and coaxial to said cylindrical orifice for receiving therefrom astream of said first plastic material, said two stationary membersdefining an axial space therebetween,

an annular channel formed in one of said stationary members, coaxiallyto its cylindrical opening and in outwardly spaced relationship thereto,and a feed opening in said stationary member leading into said annularchannel for feeding a pressurized second plastic material into saidchannel,

a rotatable member snugly mounted for rotation in said axial spacebetween said two stationary members, a bore within said rotatable memberhaving a cylindrical wall material from said annular channel into saidpassageway and forcing it therefrom into said strand of first plasticmaterial.

4. The extrusion head of claim 3, which has a stationary cylindricalmandrel coaxially disposed within the axial cylindrical opening andextending through the stationary member and through the rotatablemember.

1. In an extrusion head for continuously extruding a strand consistingof two different plastic materials: an extrusion die converging into acylindrical extrusion orifice for extruding a first plastic material; atleast one stationary member having an axial cylindrical opening alignedwith and coaxial to said cylindrical orifice for receiving therefrom astream of said first plastic material, said stationary member defining afitting surface; an annular channel formed in said fitting surface ofsaid stationary member coaxially to said cylindrical opening and inoutwardly spaced relationship to the axial cylindrical opening in saidstationary member, and a feed opening in said stationary member leadinginto said annular channel for feeding a pressurized second plasticmaterial into said channel; a rotatable member mounted for coaxialrotation around said axial cylindrical opening and to snugly fit saidfitting surface, a bore within said rotatable member having acylindrical wall flush with the inside surface of said axial cylindricalopening in said stationary member; a passageway in said rotatable memberleading inwardly to said cylindrical wall and outwardly to communicatewith said annular channel; and a vane member formed on said rotataBlemember for rotation therewith, said vane member snugly fitting into theinside of said annular channel for continuously diverting upon rotationof said rotatable member said pressurized second plastic material fromsaid annular channel into said passageway and forcing it therefrom intosaid stream of first plastic material.
 2. The extrusion head of claim 1,which has a stationary cylindrical mandrel coaxially disposed within theaxial cylindrical opening and extending through the stationary memberand through the rotatable member.
 3. In an extrusion head forcontinuously extruding a stream consisting of two different plasticmaterials: an extrusion die having a die passage converging into acylindrical extrusion orifice for extruding a first plastic material,two stationary members having each an axial cylindrical opening alignedwith and coaxial to said cylindrical orifice for receiving therefrom astream of said first plastic material, said two stationary membersdefining an axial space therebetween, an annular channel formed in oneof said stationary members, coaxially to its cylindrical opening and inoutwardly spaced relationship thereto, and a feed opening in saidstationary member leading into said annular channel for feeding apressurized second plastic material into said channel, a rotatablemember snugly mounted for rotation in said axial space between said twostationary members, a bore within said rotatable member having acylindrical wall flush with the inside surfaces of said axialcylindrical openings in said two stationary members, a passageway insaid rotatable member leading inwardly through said cylindrical wall andoutwardly to communicate with said annular channel and a vane memberformed on said rotatable member for rotation therewith, said vane membersnugly fitting into the inside of said annular channel for continuouslydiverting, upon rotation of said rotatable member, said pressurizedsecond plastic material from said annular channel into said passagewayand forcing it therefrom into said strand of first plastic material. 4.The extrusion head of claim 3, which has a stationary cylindricalmandrel coaxially disposed within the axial cylindrical opening andextending through the stationary member and through the rotatablemember.